A basepair is a pair of nucleotides on opposite complementary DNA or RNA strands which are connected via hydrogen bonds.
if your reading this it is wrong
The Complementary base pairing of DNA is A with T and C with G. In Rna, T is replaced with U.
In a strict sense no. mRNA always consists of a single RNA strand. In another sense, yes. Nuclei acids are inherently unstable in a single stranded state - the nitrogenous bases will spontaneously basepair with any nucleotides they encounter. As a result, most RNAs will spontaneously fold back on themselves, the single RNA strand basepairing with other regions of itself. That said, because the sequence will never be perfectly complementary, it's unlikely that much of the mRNA will be double stranded, but it will probably have a few segments with a double stranded character.
It depends what you mean by double stranded. If you mean two separate RNA strands, perfectly complementary to one another and existing as a basepaired structure in the cytoplasm, then no. Double stranded RNA like that only occurs in some types of viruses (and cells infected by them... so I guess the cytoplasm of a cell infected by a double stranded virus might have a lot of this kind of double stranded RNA). However, if you mean double stranded in the sense of a single RNA molecule folding back on itself and basepairing with itself - forming stem loops and more complicated structures - that kind of RNA double-strandedness is extremely common. All tRNA's and rRNA's for example exhibit this kind of double-strandedness. Nucleic acids are unstable in single stranded states and will spontaneously fold back on themselves if there is no other strand to basepair with. Nucleic acids are inherently unstable in a single stranded state. Thus,